Magnetic Resonance Imaging of the Sacroiliac Joints Indicating Sacroiliitis According to the Assessment of SpondyloArthritis international Society Definition in Healthy Individuals, Runners, and Women With Postpartum Back Pain

Abstract

ObjectiveTo compare magnetic resonance images (MRIs) of the sacroiliac (SI) joints of healthy subjects and individuals with known mechanical strain acting upon the SI joints to those of patients with axial spondyloarthritis (SpA) and patients with chronic back pain.MethodsThree readers who had received standardized training and were blinded with regard to study group randomly scored MRIs of the SI joints of 172 subjects, including 47 healthy individuals without current or past back pain, 47 axial SpA patients from the Spondyloarthritis Caught Early (SPACE) cohort (with a previous MRI confirmed positive for sacroiliitis), 47 controls with chronic back pain (irrespective of MRI results) from the SPACE cohort, 7 women with postpartum back pain, and 24 frequent runners. MRIs were scored according to the Assessment of SpondyloArthritis international Society (ASAS) definition and Spondyloarthritis Research Consortium of Canada (SPARCC) index.ResultsOf the 47 healthy volunteers, 11 (23.4%) had an MRI positive for sacroiliitis, compared to 43 (91.5%) of 47 axial SpA patients and 3 (6.4%) of 47 patients with chronic back pain. Three (12.5%) of the 24 runners and 4 (57.1%) of the 7 women with postpartum back pain had a positive MRI. Using a SPARCC cutoff of ≥2 for positivity, 12 (25.5%) of 47 healthy volunteers, 46 (97.9%) of 47 positive axial SpA patients, 5 (10.6%) of 47 controls with chronic back pain, 4 (16.7%) of 24 runners, and 4 (57.1%) of 7 women with postpartum back pain had positive MRIs. Deep bone marrow edema (BME) lesions were not found in healthy volunteers, patients with chronic back pain, or runners, but were found in 42 (89.4%) of 47 positive axial SpA patients and in 1 (14.3%) of 7 women with postpartum back pain.ConclusionA substantial proportion of healthy individuals without current or past back pain has an MRI positive for sacroiliitis according to the ASAS definition. Deep (extensive) BME lesions are almost exclusively found in axial SpA patients.

What Level of Inflammation Leads to Structural Damage in the Sacroiliac Joints? A Four‐Year Magnetic Resonance Imaging Follow‐Up Study of Low Back Pain Patients

“…Similar results were observed by de Winter et al in LBP patients, in runners, and in other healthy controls . Interestingly, de Winter and colleagues also found that BME occurring throughout the SI joints and deep lesions (depth ≥1 cm) were predominantly seen in SpA patients . The observations from these studies , together with our observations, may support the notion that local BME could be stress‐related, possibly affecting specific local “load areas” at the SI joints, while BME related to a systemic disease may cover a more extensive area and lead to structural lesions.…”

“…In a study by Weber et al that investigated physically active healthy young individuals, the authors found that, when present, BME was primarily seen at low levels and clustered topographically in distinct SI joint regions . Similar results were observed by de Winter et al in LBP patients, in runners, and in other healthy controls . Interestingly, de Winter and colleagues also found that BME occurring throughout the SI joints and deep lesions (depth ≥1 cm) were predominantly seen in SpA patients .…”

Positive HLA‐B27 and sacroiliitis is not always spondyloarthritis

“…However, unlike SpA, joint space narrowing and ankylosis do not develop . Similar to the caution about a positive HLA‐B27 and radiographic sacroiliitis, not all bone marrow edemas on MRI are SpA as it has also been reported in healthy individuals, runners and post‐partum females …”

2019 Update of the American College of Rheumatology/Spondylitis Association of America/Spondyloarthritis Research and Treatment Network Recommendations for the Treatment of Ankylosing Spondylitis and Nonradiographic Axial Spondyloarthritis

“…For patients with nonradiographic axial SpA, the imaging should focus on the sacroiliac joints. In interpreting MRI results, it is important to keep in mind the range and frequency of abnormalities, including bone marrow edema lesions, that may occur in individuals without axial SpA and that may not represent inflammation due to axial SpA . MRI is not recommended in patients in whom disease activity is either clearly clinically active or clinically stable, or when the results of MRI would not be expected to change treatment.…”